It’s not clear why, but researchers from the Mayo Clinic have confirmed that people with Parkinson’s disease are at a higher risk for melanoma. Furthermore, the link goes the other way too - people with melanoma seem to be at a higher risk for Parkinson’s disease.
Parkinson’s disease affects about 1 million Americans, and is characterized by progressive neurodegeneration, causing severe impairments in movement. Most often, the disease is associated with uncontrolled tremors; however, patients can also suffer from muscle stiffness and the difficulty moving or speaking. Because the disease is progressive, symptoms worsen over time.
Aside from the neuromuscular defects, researchers have also noticed that patients with Parkinson’s disease seem to have a higher incidence of melanoma, a deadly form of skin cancer. In particular, some studies implicated the Parkinson's drug levodopa in making patients more susceptible to developing melanoma. But the evidence against levodopa are scant, and some studies noted the link between the two diseases even in the absence of levodopa.
To fully understand the link between Parkinson’s and melanoma, researchers from the Mayo Clinic analyzed patient data in the Rochester Epidemiology Project database. They analyzed melanoma risk in 974 patients with confirmed Parkinson’s disease versus 2,922 unaffected people. At the same time, the team analyzed Parkinson’s disease risk in a group of 1,544 patients with melanoma.
The analysis confirmed the link previously noted between Parkinson’s disease and melanoma. Specifically, patients with Parkinson’s disease were four times more likely to develop the skin cancer. In addition, the results do not support the drug levodopa as a culprit in the association, as the link seems to go both ways. That is, patients with melanoma are also four times more likely to develop Parkinson’s disease.
Although the study establishes a link between the two diseases, it does not provide a biological mechanism behind the association. However, the results suggest that patients who have one disease should be closely monitored for the other disease.
"Future research should focus on identifying common genes, immune responses and environmental exposures that may link these two diseases," says first author Lauren Dalvin, M.D., a Mayo Foundation Scholar in Ocular Oncology. "If we can pinpoint the cause of the association between Parkinson's disease and melanoma, we will be better able to counsel patients and families about their risk of developing one disease in the setting of the other."
Additional source: MNT